Experimental Study On Optimization Of Energy Dissipation And Erosion Control Of Drainage Structure Of Xinjiang Subashi Reservoir

The energy dissipation and erosion control works of the hydro-junction project is of great significance to improve the flow regime and slow down the erosion of the downstream channel caused by the discharged flow.Based on the phenomenon that the mainstream downstream of the flood discharge and sand sluice gate of Subashi Reservoir was concentrated on the right bank,that the flow velocity was large,that the side wall of the right bank and the downstream were severely scoured,the hydraulic model experiment research was carried out in the present paper.The overcurrent capacity of the original design was verified through the model test.Simultaneously,the flow regime,velocity distribution,cross-section water depth,pressure,and scouring characteristics were observed.Through the collation and analysis of the measurement data,the problems of the original design scheme were found.After proposing different solutions,each scheme was verified by the model test,and finally the conclusions of the optimized scheme were reached.The results show that:(1)The discharge capacity of the current discharge structure meets the design requirements.With the increase of the flow rate,the water flow along the riverway is always partial to the right bank,local backflow phenomenon occurs in the stilling pool section,and the effect of energy dissipation is not satisfactory.Meanwhile,deflected flow to some extent occurs from the end of stilling basin to the end of concrete apron.The flow regime is turbulent,and the flow velocity at the exit of the apron is relatively high,which scours severely on the right bank wall of the drainage structure,the riverbed at the exit of the apron and the anti-scouring wall of the traffic bridge.(2)The twist sill can play the role of diversion,and the combination with the stilling sill can effectively guide the mainstream to the middle of the riverway,but cannot effectively reduce the flow velocity at the end of the apron and the erosion of downstream riverway.The guiding sill combined with the stilling sill has a better energy dissipation effect,which can effectively dissipate the flow energy,so that the flow velocity and water depth are evenly distributed in the cross section and the exit velocity of the apron is greatly reduced.However,due to the restricted actual project height,it is not recommended.(3)There are totally four stilling sills arranged in the optimization scheme.The flow hits the sills to produce overturning,which has obvious effect of energy dissipation.After the mainstream flows through the stilling basin section,it shifts to the middle and left bank with well-improved flow regime.When the last stilling sill is rotated around the vertical line of the sill center by 10°,the flow in the concrete apron section can be evenly distributed,and the water flow velocity at the downstream apron outlet can be reduced from 6.45m/s to 4.464m/s,which slows down the downstream riverbed erosion and provides a reference basis for engineering design.